This invention relates generally to a retaining device for retaining a collapsible tube in a rolled condition.
Collapsible tubes are well known in the container art for packaging semi-liquid or paste-like products. Collapsible tubes provide a convenient package which can be filled with the semi-liquid or paste-like material such as toothpaste in a mass production process. These tubes are formed of plastic coated flexible metal based materials or plastic. The metal based materials become prone to rupture upon repeated flexing or crinkling and tend to retain a shape into which it is squeezed. The tubes made of plastic materials do not rupture as readily as metal tubes and have shape memory which tends to return the tube to its original shape after squeezing. The tube is filled with material through a large end which is sealed by way of adhesive, heat sealing or folding and crimping. A reduced diameter cap end is formed with an aperture opposite the large end to provide controlled dispensing of the material therein.
Material is dispensed from the tube by removing a cap covering the cap end and squeezing the tube to force the material out through the uncovered cap end aperture. The amount of force required to dispense material from the tube depends in part on the viscosity of the material inside the tube and the amount of pressure applied to the tube. As a result of repeated use, a portion of the total volume of the material retained in the tube is dispensed. The plastic tubes tend to return to the "as formed" shape leaving a void inside of tube. The void is filled with air which may damage the portion of the material remaining in the tube. Further, if a metal based tube is repeatedly folded or crinkled while squeezing the tube may tear along stress points developed therein.
Unless a tube is systematically rolled up while dispensing, it becomes increasingly difficult to force a desired amount of material out of the tube since the paste-like material is non-uniformly distributed in the void or between opposed collapsed walls. Dispensing of the remaining volume of the material retained in the tube becomes more difficult as the remaining volume decreases with each use. Often a user will squeeze a middle portion of the tube resulting in collapse of the middle portion as opposed to the tail being collapsed. Failure to maintain the tube in a condition where the remaining material is urged towards the cap may result in damage to the tube upon repeated use or wasting of the material retained inside of the tube.
Attempts have been made to overcome the above-noted problems by providing devices which roll up the collapsed portion of the tube from a tail portion. Rolling up the exhausted portion of the tube in an organized manner assures that the maximum volume of the material retained in the tube is dispensed therefrom by forcing material from between collapsed walls towards the cap end. Further, organized rolling up of the exhausted portion of the tube prevents damage or rupture of the tube walls in metal tubes which could be caused by repeated flexing of the tube material resulting from attempts to squeeze or compress already compressed or distorted tube walls.
An example of a device employed in rolling up collapsible tubes is shown in U.S. Pat. No. 951,132 to Kinsey. The device shown in Kinsey is a key-like device which has a long narrow slot axially formed in a shaft portion for receiving an end of the tube. The end of the tube retained in the slot is rolled by axially rotating the shaft thereby rolling up the exhausted portion of the tube in an organized manner.
A device shown in U.S. Pat. No. 2,903,162 to Regan performs the same purpose in a similar way. However, the device in Regan provides a key which winds up the collapsed tube and also which locks the tube in the rolled up condition to prevent unraveling of the roll. The unraveling preventing function of this device is desirable. Unravelling may occur when pressure on the tube creates a back pressure on the material forcing the material in to the rolled portion or when the memory of the tube material returns the tube to the "as-formed" shape. While such an unraveling function is desirable, such a device is relatively expensive to produce and employs multiple discrete parts some of which are moving parts.